//
// Created by baoch on 2024/10/8.
//
#include<stdio.h>
int main() {
    double p, w;
    int s;
    scanf("%lf %lf %d", &p, &w, &s);
    if (s < 250) {
        double f1 = p * w * s * 1;
        printf("%.4lf\n", f1);
    }
    if (250 <= s && s <= 500) {
        double f2 = p * w * s * (1-0.02);
        printf("%.4lf\n", f2);
    }
    if (500 <= s && s <= 1000) {
        double f3 = p * w * s * (1-0.05);
        printf("%.4lf\n", f3);
    }
    if (1000 <= s && s <= 2000)
    { double f4 = p * w * s * (1-0.08); printf("%.4lf\n",f4);}
    if (2000 <= s && s <= 3000)
    {double f5 = p * w * s * (1-0.1); printf("%.4lf\n",f5); }
    if(3000 <= s)
    {double f6 = p * w * s *(1- 0.15); printf("%.4lf\n",f6);}
    return 0;


}